56 Background: Intracellular oncoproteins such as NY-ESO-1 and WT1 are widely distributed in different cancers and ranked as number 1 and 10 prioritized cancer antigen by international experts. It is difficult to target these antigens due to the intracellular nature by conventional antibodies. Methods: Here we reported the development of antibodies to target intracellular antigens, the same way as TCR does, recognizing MHC complex with peptides derived from intracellular oncoproteins. Phage display libraries were screened out against HLA-A2 assembled with different peptides from both WT1 and NY-ESO-1. Antibodies were tested to bind to corresponding HLA-A2/peptides complex on ELISA and FACS and finally the ability to bind to paraffin samples derived from malignancy cancer patients were confirmed. Results: We have identified several antibodies that specifically recognize the corresponding HLA-A2/peptide. Particularly, 2F4 and 1H1 could bind to RMFPNAPYL of WT1 HLA-A2 monomer on ELASA assay, by contrast the antibody did not bind to 5 other non-related HLA-A2 monomers. Furthermore, on FACS assay, both antibodies bound to WT1 peptide loaded T2 cells that express empty HLA-A2 complex on the surface. 2F4 could be routinely expressed as Fc fusion protein and maintained TCR-like feature and could recognize tumor cell lines expressing both HLA-A2 and WT1 antigen on FACS analysis. Both antibodies bind to HLA-A2/ WT1 with the affinity ranging between 10-8 and 10-9 M by Biacore analysis. Finally, paraffin sections from esophageal cancer patients were stained with antibody specific to HLA-A2/RMF and about 30% of samples shown strong reactions and The antibody to HLA-A2/SLL ( NY-ESO-1) shown a similar results although weaker stains due to the lower affinity of the antibody. Conclusions: Intracellular oncoproteins could be targeted by antibodies recognizing HLA associated with the onco-peptide processed. These antibodies have potential applications on CAR-T cell therapy or the development of bi-specific therapeutics for a number of malignancy tumors.